For first-time visitors here, Australia's wildlife - from the platypus and the thorny devil to the cassowary and the koala - seems almost indescribably exotic. This is not only true for its plants and animals but also for its landscapes and environments. The unusual fauna, unusual environments, unusual climate, and the vast size of Australia - spanning tropical rainforest and savannah woodlands in the north, through deserts, beaches and gum forests to cool alpine meadows and snowy mountaintops in Tasmania - have all combined to create and incredible diversity of species, which mark Australia out as one of the world's 'megadiverse' nations - those that occupy a total of less than 10 per cent of the world's surface area, yet together hold more than three quarters of its species. Join Australian Geographic as we take you on a pictorial journey of our fascinating world of wildlife.